A lot of my clients are curious over the “degree” use to calculate the 宅命 Home Destiny. My clients pointed out to me some confusion over what they read via web. Here i attempt to explain but is not going to be easy to understand without some fengshui fundamentals.
The example here is Northeast sector which in Period 8 the most powerful zone.
The 2 solid yellow lines showing 22.5 and 67.5 degree is the boundary of the entire Northeast sector or Chinese call it 艮卦. Some place as 22.4 or 22.45 or 22.6 degree; here i am not going to split hair over such trivial. The idea is to give you the correct perspective.
Orientation at this boundary lines 22.5 & 67.5 degree is very bad in feng shui because of 出卦空亡. It means the boundary between 2 sectors where one cannot classify under which one.
The degree 37.5 and 52.5 degree on boundary lines within the Same sector (in this example Northeast) is known as 骑线空缝 are bad.
In order to achieve good stable feng shui destiny in Period 8 using the same example 丑山未向 one have to ensure the degree should fall within 25.5 to 34.5 degree 丑山-9 degree segment and the opposite direction of Southwest segment 205.5 to 214.5 degree 未山-9 degree segment. In the picture indicate as blue 4.5 degree each way of 30 degree making it a 9 degree segment. In feng shui lingo is call 下卦
So if the degree falls between 22.5 to 25.4 or 34.4 to 37.5 degree is under 玄空替卦 calculation. Luckily for period 8 it is the same destiny. However having these 2 degree is a close call because the master need to be extremely accurate with the luo pan without any allowance for error within the 3 degree tolerance.